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Hello: I own a 2004 alumacraft 165cs navigator weight 880lbs, it has 2 group 27 trolling motor batteries up front and it is powered by a 2004 df70, this is my second season with this unit and i am not happy with the performance of it. I first read the sticky on motor height and i moved mine up 2 hole so it is in the 4th hole from the top now and running the same prop 13 and a quarter x 17 i cannot reach 30 mph on my gps at 5000 rpm.from my notes from lat year with the motor down 2 holes the results were the same although i had a full tank of fuel for this test. the boat is rated for a 75hp so it is not that undermotored,very unhappy with the top speed and i am surely lugging the motor, i can raise it one more hole but i think the next step will be to try a 13 pitch 14 dia. prop to get the rpms up and top speed, i figured i should be running at 35-38 mph@5800rpm, any help would be greatly appreciated
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It does sound like you are badly over-propped. What revs at WOT did you get before adding the 2 x batteries? That is a lot if extra weight up front.....
Every inch less of pitch gives you about 150-200 rpm, so you can work it out from there. -
i do not know as that was how it came when i bought it used. i can come up one more hole with the motor and i think i will order the 13 and a half x 13 pitch prop.Comment
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I am assuming that the engine is running well? No misfiring etc? Compression etc all good?
If that is all good then it points to incorrect propping.Comment
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being a tiller guy for years,new to controls could it be stretched throttle cables? the old timer i bought the boat from sure didn't seem like a guy who would start messing with props and top speed/rpms. the motor runs like a dream nice and smooth first crank and fires right up.Comment
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well I have a new 13 pitch prop on the way from prop depot, will give it a shot before I move up the motor to the last hole. going from a 17"pitch down to this 13" should give me a 400-500 increase in Rpm, not sure what it will do to my top end speed.Comment
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Well guys, i installed and ran the new 13 pitch this weekend. at first i noticed she really responded quicker and even sounded different and as i gave it throttle i could see my rpm;s climbing and maxing out right at 6000 but i cannot break 30mph!! i am at a complete loss now, i guess i will keep this new prop installed and i cannot come up another hole on the transom so i guess she will not get me the 35mph that i thought i SHOULD get out of herComment
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Still doesnt sound quite right.
But I really dont know your boat and how much stuff and weight you have accumulated in there! LOL we all tend to do it hey, before long we have anchors, ropes and chains, sinkers, tackle, ice boxes, batteries, etc etc in there and that weight can affect speed.
The good side is that it is now responding to throttle much better. That plus it is now not lugging. That is a big positive step.
Did You check that it is actually getting full throttle? And, it is a 13 year old motor, so a good tune up and compression test, along with hugh and low pressure fuel Filters changed etc.
I take it you have it trimmed all the way out at WOT?? With the engine now set higher, response to trim should be better too.
If that is all good, not much more you can do.Comment
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